82 GENERAL ANATOMY OF THE GLANDULAR SYSTEM. 



Of all the various opinions entertained, that of Malpighi 

 according to Miiller, was nearest the truth ; viz. that the elemen- 

 tary parts of all glands, the so named acini or granules, have 

 the same structure as the simple and compound follicles or folli- 

 cular glands, each one consisting of several minute, roundish 

 sacs, which receives its secretion from the blood-vessels distributed 

 on its walls, and which secretion is poured out through the 

 efferent duct. But these cavjties, which Malpighi believed to 

 be single elementary follicles, and Mascagni and Cruikshank 

 simple cells, have been shown by Miiller, to consist of an aggre- 

 gation of many minute ramifications of the duct, which terminate 

 by closed or coecal pouches, as is seen in fig. 144, upon which 

 the vessels ramify, and which constitute the real elementary parts 

 of the gland. 



Fig. 144.* The individual forms, which these mi- 

 nute ramifications of the secretory ducts 

 assume, vary, however, somewhat in the 

 different glands, though they are alike in 

 the general result ; that of forming an in- 

 dependent system of tubes, ramifying so 

 as to gain a great extent of surface for 

 their lining membrane. The finest se- 

 creting tubes, which are closed at their 

 extremities like the follicles of the simple mucous membranes, 

 are never, however, as has been proved by microscopical mea- 

 surement, so minute as the compound follicle, in which there 

 is a single duct common to several exceedingly minute follicles 

 of the simple kind ; which seem to be formed by the amplifica- 

 tion of the surface of a simple follicle, depressed on its sides 

 into a number of cellular dilatations which open through the 

 common duct. Specimens of these, are to be found in the 

 Meibornian glands, the tonsil, labial, buccal, duodenal glands, 

 etc. 

 In other more complicated glands, is found a further devel- 



* This is a magnified representation after Weber, of a portion of a parotid 

 gland. The smaller figure is the natural size of the piece magnified, a, The 

 cells clustered on the extreme branches of the duct of Steno. p. 



